Don't draw the trailing space of wrapped right-to-left lines (#1422)

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ### Unreleased
 
+- Fix wrapped right-to-left text shaped as one run, e.g. Arabic with `features`, drawing the space at the end of each line on its left, which pushed every line but the last one space past the right margin with `align: 'right'`. Fixes #1422
 - Fix the underline, strike-through, link and `goTo` rectangle of text drawn with a `baseline` other than the default sitting an ascent too low, because they were placed from the top of the line while the glyphs had moved up with the baseline. Fixes #994, #1245
 - Fix links to a named destination going nowhere in readers that look the name up in sorted order, such as Chrome (PDFium) and qpdf, because name tree keys were sorted by locale with `localeCompare` instead of by their bytes: with destinations named `appendix` and `Chapter1`, `Chapter1` was written second and could not be found. The keys of the `EmbeddedFiles` and `JavaScript` name trees are sorted the same way
 - Escape document information in XMP metadata and omit characters XML 1.0 cannot represent, without changing the PDF Info dictionary. Fixes #1817

lib/mixins/text.js

@@ -707,7 +707,10 @@ export default {
         positions[positions.length - 1] = space;
       }
     } else {
-      [encoded, positions] = this._font.encode(text, options.features);
+      // Don't draw the whitespace at the end of a wrapped line. The alignment
+      // above leaves it out, and right-to-left text puts it on the left.
+      const drawn = options.width ? text.replace(/\s+$/, '') : text;
+      [encoded, positions] = this._font.encode(drawn, options.features);
     }
 
     const scale = this._fontSize / 1000;

tests/unit/text.spec.js

@@ -337,6 +337,29 @@ Q
       expect(lines).toEqual(['a ', 'design-system']);
     });
 
+    test('right-to-left wrapped lines do not draw their trailing space - issue #1422', () => {
+      document.font('tests/fonts/NotoKufiArabic-Subset.ttf', 12);
+      const features = ['rtla'];
+      const [[space]] = document._font.encode(' ', features);
+      const glyphs = [];
+      const addContent = document.addContent;
+      document.addContent = function (data) {
+        if (data.endsWith('TJ')) {
+          glyphs.push(data.match(/<([0-9a-f]+)>/)[1].match(/.{4}/g));
+        }
+        return addContent.call(this, data);
+      };
+
+      document.text('هذا نص عربي', { width: 60, align: 'right', features });
+
+      // The trailing space of the first line comes first once the line is
+      // reversed, and would push the line one space past the right margin.
+      expect(glyphs).toHaveLength(2);
+      expect(glyphs[0]).toHaveLength(6);
+      expect(glyphs[0][0]).not.toBe(space);
+      expect(glyphs[0]).toContain(space);
+    });
+
     test('a continued segment can switch to lineBreak whitespace', () => {
       const lines = [];
       const line = document._line;